12 research outputs found
On local-hidden-variable no-go theorems
The strongest attack against quantum mechanics came in 1935 in the form of a
paper by Einstein, Podolsky and Rosen. It was argued that the theory of quantum
mechanics could not be called a complete theory of Nature, for every element of
reality is not represented in the formalism as such. The authors then put forth
a proposition: we must search for a theory where, upon knowing everything about
the system, including possible hidden variables, one could make precise
predictions concerning elements of reality. This project was ultimatly doomed
in 1964 with the work of Bell Bell, who showed that the most general local
hidden variable theory could not reproduce correlations that arise in quantum
mechanics. There exist mainly three forms of no-go theorems for local hidden
variable theories. Although almost every physicist knows the consequences of
these no-go theorems, not every physicist is aware of the distinctions between
the three or even their exact definitions. Thus we will discuss here the three
principal forms of no-go theorems for local hidden variable theories of Nature.
We will define Bell inequalities, Bell inequalities without inequalities and
pseudo-telepathy. A discussion of the similarities and differences will follow.Comment: 7 pages, no figure, replaced "Bell inequalities" with "Bell theorems"
and updated the reference
Large violation of Bell inequalities with low entanglement
In this paper we obtain violations of general bipartite Bell inequalities of
order with inputs, outputs and
-dimensional Hilbert spaces. Moreover, we construct explicitly, up to a
random choice of signs, all the elements involved in such violations: the
coefficients of the Bell inequalities, POVMs measurements and quantum states.
Analyzing this construction we find that, even though entanglement is necessary
to obtain violation of Bell inequalities, the Entropy of entanglement of the
underlying state is essentially irrelevant in obtaining large violation. We
also indicate why the maximally entangled state is a rather poor candidate in
producing large violations with arbitrary coefficients. However, we also show
that for Bell inequalities with positive coefficients (in particular, games)
the maximally entangled state achieves the largest violation up to a
logarithmic factor.Comment: Reference [16] added. Some typos correcte
Overshooting and semiconvection: structural changes and asteroseismic signatures
Overshooting and semiconvection are two poorly known mechanisms which affect the extent and the efficiency of chemical mixing outside classical convection zones in stars. We discuss the uncertainties and the inferences of those processes in main sequence stars burning hydrogen in a convective core. We then focus on the asteroseismic signatures of partially or fully mixed zones surrounding the convective core, through the detailed shape of the induced chemical composition profile. We emphasize the potential power of asteroseismology to determine the internal structure of stars and thus to help us understand the physical processes at work inside the stars
Distributed quantum computing
Abstract. Quantum computing combines the framework of quantum mechanics with that of computer science. In this paper we give a short introduction to quantum computing and survey the results in the area of distributed quantum computing and its applications to physics.